1. Field of the Invention
The present invention generally relates to medical patches, and more specifically relates to placement devices and related methods that enable patients to align and apply a series of medical patches over target locations on a body without the assistance of a second person or medical personnel.
2. Description of the Related Art
Nerves are part of the peripheral nervous system of a human body. They convey sensory signals back and forth from the skin and body organs to the central nervous system. Nerves may become damaged due to wear and tear, physical injuries, infection, and/or the failure of the blood vessels surrounding the nerves. These functional defects may be accompanied by pain, numbness, weakness, and in some cases, paralysis. Other problems resulting from damaged nerves may include urinary and fecal incontinence.
Different tactics have been developed to treat the above-mentioned problems. For example, treating urinary incontinence may involve behavior modification such as urinating more frequently and wearing protective undergarments. In certain social situations, however, individuals may not be able to follow the practice of frequent urination or wearing protective undergarments. Another approach involves a medical therapy including taking prescribed drugs. This methodology may result in adverse side effects or drug interactions, however, that will ultimately require discontinuation.
Another technique for treating the above-noted conditions involves stimulating a nerve using an electro-medical device that is positioned near a target nerve. One such electro-medical device is commonly referred to as an Implantable Pulse Generator (IPG), which typically includes one or more electrodes, an electrical pulse generator, a battery, and a housing. The electrical pulse generator generates an electrical signal adapted to stimulate a target nerve. When the electrodes receive the signal from the generator, they draw energy from the battery and generate an electric field of suitable strength to stimulate the target nerve.
IPG's have proven to be somewhat effective for stimulating nerves, however, they are extremely invasive because they must be implanted inside a patient's body during a surgical procedure. IPG's also consume a significant amount of power, which may be due to an increase in electrical impedance between the electrodes, or an increase in electrical impedance between the electrodes and the IPG. Higher battery power consumption may also be caused by a phenomenon referred to as “desensitization of stimulus,” whereby the human body responds to an applied external charge by offering a resistance to the applied external charge. The body resists the applied external charge by increasing the stimulation threshold for a target nerve, thereby rendering the earlier stimulus level ineffective. To overcome this problem, a more powerful charge must be generated, which consumes even more battery power, and which requires frequent replacement and/or recharging of the batteries.
In some nerve stimulation devices, it has been observed that the generated electric field spreads widely, affecting untargeted muscles and nerves along with the target nerve. The wide spreading of the electric field significantly reduces the strength of the electrical signal at the target nerve. In order to properly stimulate the target nerve, the strength of the electrical signal must be substantially increased, which requires the device to draw more power from the battery.
In view of the above drawbacks, there have been a number of efforts seeking to stimulate nerves in a more efficacious and non-invasive manner. For example, non-invasive selective nerve stimulation (SNS) medical patches are disclosed in commonly assigned U.S. Patent Publication Nos. 2005/0277998, filed Jun. 7, 2005, and 2006/0195153, filed Jan. 31, 2006, the disclosures of which are hereby incorporated by reference herein. Specifically, in one or more embodiments thereof, the '998 publication teaches a non-invasive, transcutaneous neurostimulation patch that generates and transmits a controlled, amplitude-modulated waveform comprising a carrier signal and a pulse envelope. The carrier waveform is designed to be of sufficient frequency to overcome attenuation due to tissue impedances. The pulse envelope contains specific pulse width, amplitude and shape information designed to stimulate specific nerves. In addition to nerve stimulation, medical patches may also be used for delivering pharmacological agents such as pain medication, drugs, and hormones.
Medical patches are often adhered to a patient's skin surface with an active or operating portion of the patch directed toward a target location on the patient. Over a period of time, the medical patches deliver the nerve stimulation or the pharmacological agents to the patient for achieving a therapeutic benefit. In some instances, a series of medical patches are applied to the patient, whereby a first medical patch applied by a medical professional is removed from a patient's skin and replaced with a second medical patch. Eventually, the second medical patch may be removed and replaced by a third medical patch and so on. The application of the second and subsequent medical patches is often done by the patient at home. Due to inexperience in properly placing replacement medical patches, the replacement medical patches may be improperly aligned over the target location on the patient, e.g. a particular nerve that is the target for nerve stimulation.
In view of the foregoing, there is a need for SNS medical patch placement devices and methods that provide for precise and repeatable placement of medical patches, whereby a series of medical patches are efficiently placed and precisely aligned over a target location on a patient's body. There also remains a need for improved medical patch systems that effectively stimulate target nerves and body parts, while not stimulating untargeted nerves and body parts. Furthermore, there remains a need for nerve stimulation devices that are less invasive, and that require less power to operate effectively, thereby minimizing the need to replace and/or recharge power sources.
There also remains a need for improved systems and methods for self-positioning and aligning medical patches that deliver pharmacological agents such as pain medication, drugs, and hormones. In addition, there is a need for placement devices that enables patients, while at home and unassisted, to self-locate and place medical patches over one or more target locations on the patient's body. In addition, there is a need for medical patch systems that enable patients to use their tactile senses to identify the various parts of the patch, especially in instances where the patches are not visible to the user.